There has been a substantial increase in the number of syphilis cases among men living with HIV -- particularly men who have sex with men (MSM) -- despite systematic risk reduction counseling in this population since 2008, according to a study conducted at a clinic in rural Pennsylvania presented at IDWeek 2014 earlier this month.

Syphilis cases were associated with non-injection drug use among men who have sex with men, and -- contrary to what one might expect -- tended to occur among younger, better-educated men.

"Men living with HIV, especially MSM, continue to engage in high-risk behaviors," said Poonam Mathur, DO, of the Hershey Medical Center, who presented the fincings. "Young, educated men living with HIV may have better access to the Internet or other venues to find sexual partners."

Background

According to data from the Centers of Disease Control and Prevention (CDC), the incidence of syphilis has been gradually increasing in the U.S. among gay and bisexual men since 2000. From 2007 to 2012, the syphilis case rate among MSM rose from around 6000 to 8000 per year in the U.S. -- and three-quarters of U.S. syphilis cases in 2012 occurred in this group. Cases among MSM have been associated both with high-risk sexual behaviors and with HIV coinfection.

The Hershey Medical Center HIV program, serving around 800 patients in south-central Pennsylvania, had been conducting annual syphilis testing of all patients since 1997. The center serves individuals residing in rural and small urban settings. In 2007, the program introduced a formalized screening program with targeted risk-reduction counseling in line with CDC guidance. They also offered counseling based on the Diffusion of Effective Behavioral Interventions (DEBI) to all HIV patients older than 18 at the point of care.

However, despite these counseling interventions, the program had clear evidence that local rates of syphilis were increasing. After the initiation of the harm reduction protocol, the case rate actually went up more than 3-fold, from 15 cases during 2002-2007 to 51 cases during 2008-2013.

But the reasons for the resurgence of syphilis among this population were not well understood, particularly outside of a large urban setting.

The Study

In order to better understand the epidemiology of syphilis among rural men living with HIV and to develop more effective prevention strategies in clinical care, the researchers performed a retrospective cohort study to examine factors associated with syphilis infections in HIV positive men living in south-central Pennsylvania over the period of January 2008 through June 2013.

The researchers gathered data on patient characteristics and performed a multivariable logistic regression analysis to identify factors associated with syphilis, comparing characteristics between men with and without syphilis.

The study included 702 men with HIV. Most (72%) were sexually active and a majority (67%) were MSM. The mean age was 49 years and 63% had been infected with HIV for more than 10 years. 66% had a history of non-injection drug use and 53% had a history of mental health conditions.

Results

There were 51 new syphilis diagnoses among 45 HIV positive men during following (including 5 men with 2 or more episodes).

Syphilis incidence increased significantly, from 1.0% in 2008 to 3.1% in 2012.

Characteristics of HIV positive men at the time of syphilis diagnosis included:

The men who had syphilis were significantly more likely to have reported at least 1 unsafe sexual behavior -- mainly inconsistent condom use, but also more new partners, higher rates of anal sex, and having a partner who has sex outside of one's partnership.

In the multivariate analysis, HIV positive men who were younger than age 35, better educated (some college or higher), and who perceived their partners’ behaviors as likely including sex with others, had significantly higher rates of syphilis.

When the analysis was restricted to 346 sexually active HIV positive MSM, having a higher education, a history of non-injection drug use, and a partner who has sex with others were significantly associated with a higher risk of syphilis.

Discussion

Mathur suggested that in the absence of fear of HIV transmission in the current era of antiretroviral treatment, that there is "risk-reduction fatigue" among MSM.

"It is unlikely that the rising incidence of syphilis is due to improved STD screening since there was no change in screening in the HIV program," he said. "Research indicates that using the Internet to meet partners and having unprotected anal intercourse are common in rural MSM. Perhaps HIV-infected men do not believe it is necessary to practice safer sex with a partner, even though they may have sex with other people."

It should be noted that this was a single-center study with a relatively small number of syphilis cases, and that the study did not seek out more detailed information about risk behaviors. It is also limited to what participants reported about their risk behaviors, which could have been tailored to be more socially acceptable.

Nevertheless these findings suggest that something must be done to increase the effectiveness of risk reduction interventions.

"Other studies have shown decreases in high-risk behaviors and STD incidence in HIV-infected patients following risk-reduction intervention are possible when conducted in HIV care, but the steady increase in syphilis infection among HIV-infected men across the U.S. suggests that current HIV/STD prevention strategies need to be improved in response to syphilis epidemic," said Mathur.